Protein kinases are enzymes that catalyze the transfer of a phosphate group from ATP to an amino acid residue, such as tyrosine, serine, threonine, or histidine on a protein. Regulation of these protein kinases is essential for the control of a wide variety of cellular events including proliferation and migration.
Inappropriate activation of tyrosine kinases is known to be involved in a variety of disease states including inflammatory, immunological, CNS disorders, or oncological disorders, or bone diseases. See for example Susva, M., et al., Trends Pharmacol. Sci. 21 (2000) 489-495; Biscardi, J. S., et al., Adv. Cancer Res. 76 (2000) 61-119.
The tyrosine kinases are a class of protein kinases. The Src family which consists of at least eight members (Src, Fyn, Lyn, Yes, Lck, Fgr, Hck and Blk) that participate in a variety of signaling pathways represents the major family of cytoplasmic protein tyrosine kinases (Schwartzberg, P. L., Oncogene 17 (1998) 1463-1468). The prototypical member of this tyrosine kinase family is Src, which is involved in proliferation and migration responses in many cell types (Sawyer, T., et al., Expert Opin. Investig. Drugs 10 (2001) 1327-1344). Src activity has been shown to be elevated in different cancers, e.g. breast, colon (>90%), pancreatic (>90%) and liver (>90%) tumors. Highly increased Src activity is also associated with metastasis (>90%) and poor prognosis. Antisense Src message impedes growth of colon tumor cells in nude mice (Staley, C. A., Cell Growth Differ. 8 (1997) 269-274), suggesting that Src inhibitors could slow tumor growth. Furthermore, in addition to its role in cell proliferation, Src also acts in stress response pathways, including the hypoxia response. Nude mice studies with colon tumor cells expressing antisense Src message have reduced vascularization (Ellis, L. M., et al., J. Biol. Chem. 273 (1998) 1052-1057), which suggests that Src inhibitors could be anti-angiogenic as well as anti-proliferative.
Src disrupts E-cadherin associated cell-cell interactions (Avizienyte, E., et al., Nature Cell Bio. 4 (2002) 632-638). A low molecular weight Src inhibitor prevents this disruption thereby reducing cancer cell metastasis (Nam, J. S., et al., Clin. Cancer Res. 8 (2002) 2430-2436).
Src inhibitors may prevent the secondary injury that results from a VEGF-mediated increase in vascular permeability such as that seen following stroke (Eliceiri, B. P., et al., Mol. Cell. 4 (1999) 915-924; Paul, R., et al., Nat. Med. 7 (2001) 222-227).
Blockade of Src prevents dissociation of the complex involving Flk, VE-cadherin, and β-catenin with the same kinetics with which it prevents VEGF-mediated VP/edema and account for the Src requirement in VEGF-mediated permeability and provide a basis for Src inhibition as a therapeutic option for patients with acute myocardial infarction (Weis, S., et al., J. Clin. Invest. 113 (2004) 885-894).
Src also plays a role in osteoporosis. Mice genetically engineered to be deficient in Src production were found to exhibit osteopetrosis, the failure to resorb bone (Soriano, P., et al., Cell 64 (1991) 693-702; Boyce, B. F., et al., J. Clin., Invest. 90 (1992) 1622-1627). This defect was characterized by a lack of osteoclast activity. Since osteoclasts normally express high levels of Src, inhibition of Src kinase activity may be useful in the treatment of osteoporosis (Missbach, M., et al., Bone 24 (1999) 437-449).
Low molecular weight inhibitors for protein kinases are widely known in the state of the art. For the inhibition of src and other kinases such inhibitors are based on i.e. 8H-pyrido[2,3-d]pyrimidin-7-one derivatives (see e.g. WO 96/34867, WO 96/15128, U.S. Pat. No. 5,733,914, WO 02/018379, WO 02/018380, WO 2005/034869, Klutchko, S. R, et al., J. Med. Chem. 41 (1998) 3276-3292 or Blankley, C. J., J. Med. Chem. 41 (1998) 1752-1763) or 3,4-dihydro-1H-pyrimido[4,5-d]pyrimidin-2-one derivatives (see e.g. WO 99/61444, WO 00/024744, WO 01/029041, WO 01/029042, WO 2004/011465, WO 2004/041821, WO 2004/041823, WO 2004/075852, WO 2004/089955 or WO 2005/011597). Some pyrido-pyrimidinone derivatives are known from cross-coupling reaction studies (Sakamoto, T., et al., Chemical & Pharmaceutical Bulletin 30 (1982) 2410-2416).